JPH093418A - Double-sided adhesive tape - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a double-sided pressure-sensitive adhesive tape that exhibits high adhesive strength to an adherend having a low polarity surface such as a polyolefin resin. A copolymer of an acrylic acid ester monomer having an alkyl group having 1 to 14 carbon atoms and a copolymerizable monomer copolymerizable with the (meth) acrylic acid ester monomer, and having an average particle diameter of 1 to 150 μm A pressure-sensitive adhesive layer is provided on both surfaces of a base material layer composed of fine particles and having a stress relaxation rate of 50% or more after 1 hour in a 100% stretched state, and the tackifying resin of the pressure-sensitive adhesive is pentaerythritol. It is an ester, and the crosslinking agent is an aziridine compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive tape having excellent adhesive strength and capable of easily joining structures and the like, and particularly to a low-polarity surface such as polyolefin resin. The present invention relates to a double-sided pressure-sensitive adhesive tape having excellent adhesive strength to a bonded body.

[0002]

2. Description of the Related Art Conventionally, a double-sided adhesive tape having a base material made of polyethylene foam, chloroprene foam, urethane foam, acrylic foam, etc., on both sides of which an acrylic adhesive layer is provided, is used for automobiles and home appliances. It is widely used in the fields of products, office automation equipment, housing construction materials, etc. The adhesive strength such as shear strength and peeling strength of such an adhesive tape is determined by the cohesive failure strength of the base material, but there is a problem that the base material foam has a low breaking strength and a high adhesive strength cannot be obtained. there were.

Therefore, the present applicant has proposed an adhesive tape and an adhesive tape based on an acrylic sheet having a high adhesive strength (Japanese Patent Application No. 5-236370).

[0004]

[Patent Document 1] Japanese Patent Application No. 5-236
The one described in No. 370 has improved adhesive strength by mixing various fillers such as fibrous fillers and non-polar resin fine particles in the base material. However, the adhesive strength to an adherend having a low polar surface such as a polyolefin resin is insufficient.

An object of the present invention is to solve the above-mentioned conventional problems and to provide a double-sided pressure-sensitive adhesive tape which exhibits high adhesive strength to an adherend having a low polarity surface such as a polyolefin resin.

[0006]

The double-sided pressure-sensitive adhesive tape of the present invention has an acrylic acid ester monomer selected from (meth) acrylic acid esters having an alkyl group having 1 to 14 carbon atoms, a polar group, and the above ( A copolymer of (meth) acrylic acid ester monomer and one or more copolymerizable monomers copolymerizable with the copolymer, and fine particles having an average particle diameter of 1 to 150 μm, the fine particles being based on 100 parts by weight of the copolymer. 0.5 to 175 parts by weight, or 10 to 50% by volume of the above copolymer in a volume fraction, and a stress relaxation rate of 50% or more after 1 hour in a 100% stretched state. Of the (meth) acrylic acid alkyl ester having an alkyl group having 2 to 18 carbon atoms and a polymerizable unsaturated carboxylic acid in an amount of 0.5 to 10% by weight. Both An acrylic pressure-sensitive adhesive composition comprising an acrylic copolymer (A) as a main component, which is mixed with a tackifying resin (B) and a cross-linking agent (C), the tackifying resin (B ) Is a pentaerythritol ester of a polymerized rosin, a cross-linking agent (C) is an aziridine-based compound, and the compounding amounts of the tackifying resin (B) and the cross-linking agent (C) are the above acrylic copolymer in terms of solid content. (A)
5 to 40 parts by weight and 0.
It is characterized in that it is from 01 to 0.5 parts by weight.

As the (meth) acrylic acid ester having an alkyl group having 1 to 14 carbon atoms, which is used for the base material layer,
Preferably, a (meth) acrylic acid ester having an alkyl group having 4 to 12 carbon atoms is used, and specifically, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and (meth) acrylic acid. Examples thereof include isooctyl, n-octyl (meth) acrylate, isononyl (meth) acrylate, lauryl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, and hexyl (meth) acrylate. These are single or 2
More than one type can be used in combination.

Usually, in consideration of the balance between adhesiveness and cohesiveness, a homopolymer mainly comprises a (meth) acrylic acid ester having a glass transition point of -50 ° C. or lower, and a methyl (meth) acrylate, ( You may use together (meth) acrylic acid ester of lower alcohols, such as ethyl (meth) acrylate.

The copolymerizable copolymerizable monomer having a polar group includes a carboxyl group-containing monomer such as (meth) acrylic acid, maleic acid, fumaric acid and itaconic acid, or an anhydride thereof, or (meth) acrylonitrile. , N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, (meth) acrylamide, dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, dimethylaminopropylacrylamide and other nitrogen-containing monomers, 2-hydroxyethyl (meth ) Hydroxyl group-containing monomers such as acrylate, 4-hydroxybutyl acrylate, polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, and caprolactone-modified (meth) acrylate.

The (meth) acrylic acid ester monomer contained in the acrylic monomer composed of the (meth) acrylic acid ester monomer and the copolymerizable monomer is 50 to 50%.
It is preferably 98% by weight, more preferably 70 to 95% by weight. If it is less than 50% by weight, the cohesive force becomes too high and the pressure-sensitive adhesiveness is lowered. If it exceeds 98% by weight, the cohesive force becomes too low and a high shear strength cannot be obtained.

The content of the copolymerizable monomer having the polar group is 2 to 20% by weight based on the acrylic monomer.
Should be. If it is less than 2% by weight, the cohesive force is too low to obtain high shear strength, and if it exceeds 20% by weight, the cohesive force is too high and the pressure-sensitive adhesiveness is impaired.

An excellent cohesive force can be obtained by adding a crosslinking monomer to the (meth) acrylic acid ester monomer and the copolymerizable monomer having a polar group to effect crosslinking. Examples of the crosslinkable monomer include hexanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, pentaerythritol di (meth) acrylate. ) Acrylate, pentaerythritol tri (meth) acrylate, trimethylolpropane trimethacrylate, vinyl (meth) acrylate, divinylbenzene, and other epoxy acrylate, polyester acrylate and the like are preferably used. The addition amount of these crosslinkable monomers is preferably 0.01 to 1 part by weight, more preferably 0.02 to 0.8 part by weight. If the amount is less than 0.01 part by weight, the degree of crosslinking is insufficient and the necessary cohesive force cannot be obtained.
If it exceeds 1 part by weight, the crosslink density becomes high and the cohesive force is too high, so that the pressure-sensitive adhesiveness is impaired.

As the acrylic monomer constituting the base layer of the double-sided pressure-sensitive adhesive tape of the present invention, the above-mentioned (meth) acrylic acid ester, the copolymerizable monomer having a polar group, and the crosslinkable monomer are copolymerized with other monomers. It doesn't matter what you do. For example, vinyl acetate, vinyl propionate, styrene, isobornyl (meth) acrylate and the like are preferably used. The content of these other monomers is 30% by weight
Should be: If it exceeds 30% by weight, the cohesive force will be too high and the pressure-sensitive adhesiveness will be deteriorated.

In order to polymerize each of the above monomers constituting the base material layer, photopolymerization can be carried out by adding a photopolymerization initiator and irradiating with ultraviolet rays. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone (trade name "Darocur 2959" manufactured by Merck & Co., Inc.), α-hydroxy-α, α'-. Dimethyl-acetophenone (Merck, trade name "Darocur 1173"), methoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone (Ciba Geigy, trade name "Irgacure 6"
51 "), 2-hydroxy-2-cyclohexylacetophenone (manufactured by Ciba-Geigy, trade name" Irgacure 184 "), acetophenone-based photopolymerization initiators, benzoin ethyl ether, benzyl dimethyl ketal-based photopolymerization initiators, Other examples include halogenated ketones, acyl phosphino oxides, and acyl phosphonates. The above photopolymerization initiators may be used alone or in combination of two or more.

The amount of the photopolymerization initiator added is preferably 0.01 parts by weight, more preferably 0.05 to 3 parts by weight, based on 100 parts by weight of the composition containing the above-mentioned monomer. If the addition amount of the photopolymerization initiator is less than 0.01 part by weight, the polymerization conversion rate is lowered to give a polymer having a strong monomer odor, and if it exceeds 5 parts by weight, the radical generation amount is increased and the molecular weight is lowered. There is a possibility that the necessary cohesive force may not be obtained.

The base layer of the pressure-sensitive adhesive tape of the present invention is characterized by a stress relaxation rate of 50% or more after 1 hour in a 100% stretched state. The stress relaxation rate is measured by the following method. Be seen. Set the distance between the upper and lower chucks of the tensile tester to 4
A test piece having a width of 20 mm and a width of 20 mm is allowed to stand for 1 hour in a 100% stretched state, and then the stretched state is released to measure the residual stress. The stress relaxation rate is a value obtained by the following equation. [(Initial maximum stress-1 residual stress after 1 hour) / initial maximum stress] × 100

The stress relaxation rate has an important effect on the pressure-sensitive adhesive tape. That is, when two adherends are bonded as a double-sided adhesive tape, the stress relaxation characteristic of the base material layer relaxes the stress at the time of peeling from the adherend, so that the strength of the bond between the two adherends is high. Becomes When the base material layer has no stress relaxation property, the stress at the time of peeling is concentrated between the adherend and the adhesive tape, and the bonding strength is reduced.

There are several possible methods for imparting stress relaxation characteristics to the base material layer. For example, the average particle size is 1 to 150 μm.
There is a method of blending fine particles having m. The fine particles include those having a solid interior and hollow fine particles. Examples of such fine particles include glass balloons, inorganic hollow particles such as fly ash balloons, polymethylmethacrylate, acrylonitrile-vinylidene chloride copolymer, polystyrene, organic hollow particles made of phenolic resin, glass beads, silica beads, and synthetic. Examples thereof include inorganic fine particles such as mica and organic fine particles such as polyethyl acrylate, polyurethane, polyethylene and polypropylene. When the average particle size is less than 1 μm or exceeds 150 μm, high stress relaxation characteristics cannot be obtained.

The amount of the fine particles is 0.5 to 175 parts by weight based on 100 parts by weight of the monomer composition. 0.7 to 10 parts by weight is preferable for hollow fine particles having a small specific gravity, 10 to 60 parts by weight for hollow fine particles or organic fine particles having a specific gravity of about 1, and 70 to 150 for heavy inorganic fine particles having a specific gravity of 2 or more. Parts by weight are preferred. The volume fraction should be 10 to 50% by volume, and if it is less than 10% by volume or exceeds 50% by volume, high stress relaxation characteristics cannot be obtained.

A tackifying resin may be added as a composition of the base material layer. Suitable tackifying resins, rosin resins, modified rosin resins, terpene resins, terpene phenol resins, C ₅ and C ₉ petroleum resins, coumarone resins, also these water additives and the like, alone or in Used in combination. However, when these are blended in a photopolymerizable composition and subjected to a photopolymerization reaction, the polymerization rate may be decreased or the molecular weight may be decreased. In such a case, the amount of the chain transfer agent or the crosslinkable monomer may be decreased. Need to be adjusted appropriately.

The substrate layer can be manufactured with a thickness in the range of 50 μm to 5 mm. However, it is necessary to increase the viscosity so that the fine particles are well dispersed so as not to impair the surface smoothness of the fine particles or hollow fine particles, and to impart thixotropy. 1000 cp when the thickness is 100 μm or less
It can be applied even when the s and TI values are about 1.5. However, if the thickness is to be increased, the viscosity should be higher.

As a means for increasing the viscosity, an acrylic rubber, a nitrile rubber, an elastomer such as styrene-isoprene-styrene (SIS), or a thermoplastic resin such as PMMA or PSt may be dissolved, and the average diameter is 5 μm or less. Silica, alumina, etc. may be mixed. In the case of adding an inorganic substance, the one that has been subjected to the hydrophobizing treatment can be dispersed more quickly to the primary particles. It is also possible to increase the viscosity by preliminarily partially polymerizing a part of the composition without adding the above additives. Monomers that are partially polymerized should be 1.5-60% of total monomers. If it is less than 1.5%, the required viscosity cannot be obtained, and if it exceeds 60%, the viscosity becomes too high and coating cannot be performed. The above means for thickening should be done before adding the photoinitiator and prevent the formation of microgels. Partial gel formation causes defects such as streaks during coating.

For light irradiation for photopolymerization, a light wavelength of 4
A light source having a light emission distribution of 00 nm or less is used, and for example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra low pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excited mercury lamp, a metal halide lamp and the like are used. Among them, the chemical lamp efficiently emits light in the active wavelength region of the photopolymerization initiator, and since light absorption by the composition other than the photopolymerization initiator is small, light is transmitted to the inside, so a high-thick film product is recommended. Preferred for manufacturing.
The light irradiation intensity of the photopolymerizable composition by the light source is a factor that influences the degree of polymerization of the obtained polymer, and is appropriately controlled depending on the performance of the intended product, but a cleavage type having an ordinary acetophenone group. When the photopolymerization initiator of
The range is a wavelength region effective for photodecomposition of the photopolymerization initiator (usually 365 nm to 420 nm, though it varies depending on the photopolymerization initiator).
Light is used. ) Has a light intensity of 0.1 to 100 mW /
cm ² is preferred.

The photopolymerization reaction of the photopolymerizable composition is inhibited by oxygen in the air and oxygen dissolved in the photopolymerizable composition. Therefore, the light irradiation must be performed by a method that can avoid the polymerization inhibition by oxygen. One of the methods is to cover the photopolymerizable composition with a cover film such as polyethylene terephthalate or Teflon which has been subjected to surface peeling treatment,
There is a method of irradiating the composition with light through the film. Further, light may be irradiated from an optically transparent window into an inert zone in which an inert gas such as nitrogen gas or carbon dioxide gas is replaced with oxygen, and a polymerization reaction may be carried out therein. In the latter method, the oxygen concentration in the inert zone needs to be 5000 ppm or less in order to sufficiently react until the polymerization conversion rate of the composition becomes 99.7% or more.
pm or less is preferable.

When the photopolymerizable composition undergoes a rapid polymerization reaction, the release film coated with the photopolymerizable composition or the covered cover film undergoes heat shrinkage due to the heat of polymerization and is obtained. Vertical stripes may appear on the base material layer, resulting in a defective product. In such a case, it can be solved by using a heat ray-shielding filter to suppress the radiant heat from the light source, or by cooling the surface of the film opposite to the irradiation surface by contacting the cooling plate surface.

The acrylic copolymer (A) used in the pressure-sensitive adhesive layer is mainly composed of a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 18 carbon atoms, and a polymerizable unsaturated carboxylic acid It can be obtained by copolymerizing 0.5 to 10% by weight of an acid and using it alone or by polymerizing or copolymerizing the above ester and a monomer copolymerizable therewith.

As the (meth) acrylic acid alkyl ester as the main component, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, ( (Meth) acrylic acid-sec-butyl, (meth) acrylic acid-t-
Butyl, (meth) acrylic acid-n-octyl, (meth)
Acrylic acid-isooctyl, (meth) acrylic acid-2-
Ethylhexyl, (meth) acrylic acid-isononyl,
Examples thereof include lauryl (meth) acrylate and dodecyl (meth) acrylate. These may be used alone or in combination of two or more kinds. When the number of carbon atoms of the alkyl group is out of the range of 2 to 18, the characteristics as an adhesive are impaired, which is not preferable.

Examples of the polymerizable unsaturated carboxylic acid include (meth) acrylic acid and itaconic acid. The copolymerization ratio of these unsaturated carboxylic acids is preferably 0.5 to 10% by weight, particularly preferably 1 to 5% by weight. If the amount is less than 0.5% by weight, the degree of crosslinking of the pressure-sensitive adhesive does not increase and sufficient creep characteristics cannot be obtained. On the other hand, if it is more than 10% by weight, the initial adhesive strength is lowered.

The polymerization methods include bulk polymerization, solution polymerization,
A known method such as dispersion polymerization or emulsion polymerization may be adopted.
The method of initiating polymerization is a method using a thermal polymerization initiator such as benzoyl peroxide, lauroyl peroxide, azoisobutyroyl nitrile, a method using a photopolymerization initiator such as benzoin, benzoin methyl ether, benzophenone and ultraviolet irradiation or electron beam irradiation. May be arbitrarily selected. When the weight average molecular weight of the obtained acrylic copolymer is less than 200,000, the cohesive force of the pressure-sensitive adhesive decreases, so 200,000 or more is preferable.

As the polymerized rosin pentaerythritol used as the tackifying resin (B) in the present invention, specifically, trade names "Pencel D-125" and "Pencel D-13" are used.
Typical examples are "5", "Pencel D-160" (manufactured by Arakawa Chemical Industry Co., Ltd.), and "Pentaline C" (manufactured by Rika Hercules Co., Ltd.). The content of pentaerythritol in these polymerized rosins is 5 to 40 parts by weight with respect to 100 parts by weight of the acrylic copolymer. If the amount is less than 5 parts by weight, the tackifying effect of the tackifying resin cannot be obtained and the adhesion to the low-polarity free energy surface is lowered. On the other hand, if the amount is more than 40 parts by weight, the initial adhesive strength is lowered and the heat resistance is also lowered.

The reason why the aziridine compound is used as the cross-linking agent in the present invention is to increase the cohesive force and heat resistance by reacting with the carboxyl group of the polymerizable unsaturated carboxylic acid to cross-link. . The aziridine compound as the cross-linking agent (C) is a compound having two or more aziridine rings represented by the structural formula shown below,

[0032]

Embedded image

Examples thereof include phosphoric acid amides of ethylene-imine and 2-methylethyleneimine, synthetic sulfur phosphoric acid amides, polycarbamic acid amides, polythiocarbamic acid amides, cyanuric acid amides, and polyureas. Representative examples of ethylene / imine include tris (1-aziridinyl) phosphine oxide, 2,4,6-tris (1-aziridinyl) -s-triazine, diphenylmethane-bis-4,
4'-N, N'-ethylene urea, hexamethylene-bis-w, w'-N, N 'ethylene urea, tetramethylene-bis-N, N' ethylene urea, triphenylmethane-4,4 ', 4 ″ -Triethylene urea, p-phenylene bis ethylene urea, m-toluylene bis-N,
N'-ethylene urea, carbonyl bis aziridine, etc. are mentioned. Similar derivatives can be mentioned for 2-methylethyleneimine.

The amount of the above-mentioned aziridine compound to be blended is 0.1 in terms of solid content based on 100 parts by weight of the acrylic copolymer.
It is from 01 to 0.5 parts by weight. If the amount is less than 0.01 parts by weight, heat resistance cannot be obtained, and if the amount is more than 0.5 parts by weight, an excessive crosslinking reaction occurs and the initial adhesive strength cannot be obtained.

In the acrylic pressure-sensitive adhesive composition of the present invention, various conventionally known additives such as, for example,
You may mix | blend a plasticizer, a softener, a filler, a pigment, a dye, calcium carbonate, silica, talc, etc.

An adhesive strength-enhancing layer may be provided between the surface of the base material layer and the pressure-sensitive adhesive layer laminated thereon. As the adhesion enhancing layer, a polyamine compound, a polyfunctional isocyanate compound, a polyfunctional carbodiimide compound, a polyfunctional oxazoline compound, chloroprene, chlorinated natural rubber, a compound having a methylol group, a compound having a methoxymethyl group and the like are used.

[0037]

In the double-sided pressure-sensitive adhesive tape of the present invention, the base material layer has 1 carbon atoms.
It is composed of a copolymer of a (meth) acrylic acid ester monomer having an alkyl group of 14 to 14 and a copolymerizable monomer having a polar group and capable of being copolymerized with the monomer, so that pressure-sensitive adhesiveness and high shear strength are obtained. Will have. Furthermore, since the fine particles having an average particle diameter of 1 to 150 μm are blended in a specific amount with respect to the above-mentioned copolymer, the stress relaxation rate after 1 hour in a 100% stretched state is 50% or more. The cohesive failure strength of the material layer is increased and strong adhesive strength is exhibited.

The pressure-sensitive adhesive layer is made of (meth) acrylic acid alkyl ester having an alkyl group having 2 to 18 carbon atoms,
Since the main component is an acrylic copolymer obtained by copolymerizing a polymerizable unsaturated carboxylic acid in an amount of 0.5 to 10% by weight, it has a sufficient degree of crosslinking and an initial adhesive force. Furthermore, since pentaerythritol is used as the tackifying resin, it exhibits strong adhesiveness to an adherend having a low polarity surface such as a polyolefin resin. In addition, since the cross-linking agent is an aziridine compound, it has high cohesive force and heat resistance.

Therefore, when the double-sided pressure-sensitive adhesive tape of the present invention is used for joining a structure having a low polarity surface such as a polyolefin resin, excellent adhesive strength can be obtained.

[0040]

EXAMPLES Examples of the double-sided adhesive tape of the present invention will be described below. Preparation of base material layer (base material layer 1) 850 parts by weight of 2-ethylhexyl acrylate, 50 parts by weight of acrylic acid, N-vinylpyrrolidone 1
00 parts by weight, n-dodecanethiol 0.2 parts by weight, 2,
3 parts by weight of 2-dimethyl-2-phenylacetophenone (trade name "Irgacure 651" manufactured by Ciba Geigy),
420 parts by weight of high-density polyethylene fine particles with an average particle diameter of 20 μm (Mitsui Petrochemical Co., Ltd., trade name “Miperon XM-220”, specific gravity 0.95) were stirred and uniformly dispersed in a separable flask, followed by nitrogen gas. Was dissolved to remove dissolved oxygen to obtain an acrylic composition.

Next, when the above acrylic composition was irradiated with ultraviolet rays from a black light lamp, the temperature of the composition increased and the viscosity increased at the same time. The composition temperature is 5
When the temperature rose, the ultraviolet irradiation was stopped. As a result, the partially polymerized thickened composition had a conversion of 3.7% and a viscosity of 2200 cps. Further, 0.2 part by weight of hexanediol acrylate was added to the above composition.

On the polyethylene terephthalate film having a thickness of 38 μm subjected to the mold release treatment, the partially polymerized thickened composition was coated so that the thickness at the end of the polymerization would be 1 ± 0.1 mm, and the mold release treatment of the same thickness was performed. Another polyethylene terephthalate film was coated as a cover film so as to be in contact with the coated surface. The height of the lamp was adjusted using a chemical lamp so that the irradiation intensity on the surface of the cover film was ² mw / cm ^2, and light was irradiated for 8 minutes to obtain a sheet having pressure-sensitive adhesiveness. The residual monomer of the obtained base material layer was less than 0.1%, the gel fraction was 95%, and the stress relaxation rate was 75%.

(Substrate layer 2) isononyl acrylate 95
0 parts by weight, N-vinylcaprolactam 50 parts by weight, hydrophilic silica (trade name "Aerosil 2 manufactured by Nippon Aerosil Co., Ltd.
00 ") 30 parts by weight with a dissolver type agitator for 1 hour for 4 hours
The mixture was stirred and mixed at 000 rpm to obtain a viscous liquid. In addition, a glass balloon having an average particle diameter of 45 μm (made by Asahi Glass Co., Ltd., trade name “CEL-STARZ-27”, specific gravity 0.2
7) 50 parts by weight, 3 parts by weight of a photopolymerization initiator (trade name "Irgacure 651" manufactured by Ciba-Geigy Co., Ltd.), and 0.3 parts by weight of hexanediol diacrylate were added and stirred and mixed until uniform, and then nitrogen gas was added. Purged to remove dissolved oxygen. Hereinafter, in the same manner as the base material layer 1, the thickness is 1.5 m.
A base sheet having a pressure-sensitive adhesive property of m was obtained. The stress relaxation rate of the obtained base sheet having pressure-sensitive adhesiveness was 72%.

(Base material layer 3) A pressure-sensitive adhesive sheet having a thickness of 1 mm was obtained in the same manner as the base material layer 1 except that polyethylene fine particles were not mixed in the base material layer. The stress relaxation rate was 25%.

Preparation of Acrylic Adhesive (Adhesive 1) 97 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, 0.05 part by weight of lauryl mercaptan as a chain transfer agent, and ethyl acetate of 80 as a solvent.
1 part by weight was charged into a flask equipped with a stirrer, a continuous cooling tube, a thermometer and a nitrogen gas inlet so that the total amount was 1 kg, and dissolved by stirring, and then purged with nitrogen gas for about 30 minutes to exist in the monomer. Oxygen was removed. Then, the air in the flask was replaced with nitrogen gas, the temperature was raised with stirring, the temperature was maintained at 80 ° C., and 0.1 part by weight of benzoyl peroxide was added as a thermal polymerization initiator. The mixture was stirred for 8 hours for polymerization to obtain an acrylic pressure-sensitive adhesive solution. 0.1 part by weight of N, N'-hexamethylene-1,6-bis (1-aziridinecarboxide) as a cross-linking agent, and a predetermined amount of the tackifying resin shown in Table 1 were added to the acrylic adhesive solution. Then, the pressure-sensitive adhesive composition was prepared.

(Adhesives 2 to 9) An adhesive solution was prepared in the same manner as Adhesive 1 except that the formulation was as shown in Table 1.

[0047]

[Table 1]

Preparation of double-sided pressure-sensitive adhesive tape (Examples 1 to 3) The combination of the base layer and the pressure-sensitive adhesive shown in Table 2 was used, and the pressure-sensitive adhesive solution was dried on the release-treated surface of the release paper so that the thickness was 50 μm. The pressure-sensitive adhesive layer formed by coating and drying was laminated on both sides of the base material layer using a laminating machine to prepare a double-sided pressure-sensitive adhesive tape.

(Comparative Examples 1 to 7) Table 2 shows the base material layer and the adhesive.
A double-sided pressure-sensitive adhesive tape was produced in the same manner as in the example except that the combination shown in was used.

Performance Evaluation (1) Measurement of Peeling Force The double-sided pressure-sensitive adhesive tapes of Examples and Comparative Examples were cut to a width of 20 mm and a length of 150 mm, and one side thereof was 20 mm in width and 20 in length.
Adhesion length of 100 m to a 0 mm thick 2 mm thick polypropylene resin plate (manufactured by Nippon Test Panel Co., Ltd.) in an atmosphere of 23 ° C
Then, a 50 μm-thick SUS304 sheet for backing was attached to the other pressure-sensitive adhesive layer surface of the double-sided pressure-sensitive adhesive tape. After reciprocating twice from the top of the SUS304 sheet with a roller having a weight of 2 kg, the peeling force of 90 degrees was measured 24 hours later using a tensile tester at a speed of 300 m / min.

(2) Measurement of shear adhesive strength The double-sided pressure-sensitive adhesive tapes of Examples and Comparative Examples were cut into squares of 20 mm on each side, and a square polypropylene resin plate of 2 mm in thickness and 50 mm on each side (manufactured by Japan Test Panel) 2 Affixed in a sandwich form to the center of the sheet in an atmosphere of 23 ° C. and 65% RH, and apply a load of 5 kg from above the resin plate for 1
After press-bonding for 5 minutes, after 24 hours, the shear adhesive force was measured by pulling in the shearing direction at a pulling speed of 5 mm / min.

(3) Holding force test One of the polypropylene resin plates in the same state as that used for measuring the shear adhesive strength was fixed to a vertical wall surface, and a load of 3 kg was applied to the other polypropylene resin plate surface for 24 hours. The dropping state of the resin plate after the elapse of time was observed. Table 2 shows the above results.

[0053]

[Table 2]

As is clear from Table 2, the double-sided pressure-sensitive adhesive tapes of Examples 1 to 3 have excellent peeling force, shearing adhesive force and holding force. However, none of the comparative examples satisfies all of these evaluation items.

[0055]

Since the double-sided pressure-sensitive adhesive tape of the present invention has the above constitution, the base material layer has pressure-sensitive adhesiveness and high shear strength, and the base material layer has high cohesive failure strength and strong adhesive strength.
Further, the pressure-sensitive adhesive layer has a sufficient degree of crosslinking and an initial adhesive force, and exhibits strong adhesiveness to an adherend having a low polar surface such as a polyolefin resin. In addition, since the cross-linking agent is an aziridine compound, it has high cohesive force and heat resistance. Therefore, when the double-sided pressure-sensitive adhesive tape of the present invention is used for joining a structure having a low polarity surface such as a polyolefin resin, excellent adhesive strength can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area C09J 133/06 JDD C09J 133/06 JDD

Claims (1)

[Claims] 1. An acrylic acid ester monomer selected from a (meth) acrylic acid ester having an alkyl group having 1 to 14 carbon atoms, a polar group, and copolymerizable with the above-mentioned (meth) acrylic acid ester monomer. Copolymer with one or more copolymerizable monomers, and average particle size 1 to 15
0 μm fine particles, and the fine particles are the above-mentioned copolymer 1
0.5 to 175 parts by weight to 100 parts by weight, or 10 to 50% by volume of the above copolymer in a volume fraction of 100,
The stress relaxation rate after 1 hour is 50% in the stretched state.
% Of the base material layer is provided on both sides of the base material layer, and the pressure-sensitive adhesive layer comprises a (meth) acrylic acid alkyl ester having an alkyl group having 2 to 18 carbon atoms and a polymerizable unsaturated carboxylic acid. An acrylic pressure-sensitive adhesive composition comprising an acrylic copolymer (A) obtained by copolymerization of 0.5 to 10% by weight as a main component, and a tackifying resin (B) and a cross-linking agent (C) added thereto. The tackifying resin (B) is a pentaerythritol ester of polymerized rosin, the cross-linking agent (C) is an aziridine compound, and the tackifying resin (B) and the cross-linking agent (C) are mixed in solid content. A double-sided pressure-sensitive adhesive tape, which is 5 to 40 parts by weight and 0.01 to 0.5 parts by weight, respectively, with respect to 100 parts by weight of the acrylic copolymer (A).